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Queensferry

Module 07

Groundwater and layered ground

Two things the textbook equation assumes away, and both of them matter.

What this module covers

  • Explain the two separate ways a high water table reduces bearing capacity
  • Locate the water table correctly relative to the failure mechanism
  • Recognise when a strong crust over soft ground invalidates the bearing capacity equation
  • Describe punching-through failure and how it is checked

Lessons

  1. It attacks twice, and people usually remember once.

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  2. When the mechanism cannot form the way the equation assumes.

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Module checkpoint

Check what you have taken in

2 questions

  1. Question 1

    A footing has a dry ultimate capacity of 1746 kPa. With the water table at the surface it falls to 845 kPa. What is the percentage reduction, to the nearest whole number?

  2. Question 2

    Below roughly what depth does the water table stop affecting bearing capacity?